Installation of tap changing devices in transformers



March 29. 1966 Him A. LEHMANN ETAL 3,243,748

INSTALLATION OF TAP CHANGING DEVICES IN TRANSFORMERS Filed Aug. 29, 1963F/a Z 7 3. IIWJ! dmz. /hr Ester/rap United States Patent Austria FiledAug. 29, 1963, Ser. No. 305,336 Claims priority, application Austria,Aug. 31, 1962, 6,972/ 62 6 Claims. (Cl. 336-137) The present inventionrelates to the installation of tap changing devices in transformers. Inparticular, this invention relates to a special problem of transformerdesign, namely to the installation of tap changing devices withintransformer tanks having bell-shaped covers. With bell-shaped cover ismeant a transformer cover or hood, the gasket flange of which, betweenthe cover and the tank proper, runs adjacent the bottom of thetransformer tank. In other words, the cover has the appearance of a bellhooding the working or effective parts of the transformer.

This mode of tank construction has the advantage that in case of arepair, overhaul or supervisory work on the working parts of thetransformer, upon having drained the tank oil, it is only necessary tolift the comparatively light cover for which no exceptional liftingdevices are required. There are, however, some difficulties resultingfrom this tank construction in regard to the installation of tapchanging devices.

The difficulties arise from the fact that, owing to the usual attachmentof the tap changing devices on the magnetic-core clamping structurewhich is also used for clamping the windings, the tightening up of theclamping structure after baking the assembled magnetic core andwindings, level-differences result for the tap changing device relativeto the transformer bottom and cover, respectively. These leveldifferences render problematic a satisfactory sealing of the tapchanging devices passing through the trans-former cover.

In other words, the tap changing device attached to the core and windingclamping structure changes its height after the transformer baking(drying out the core and coils) while the internal tank height remainsunchanged. Consequently, difficulties result in sealing the tap changingdevice within the transformer tank.

The main object of this invention is to avoid the aforementioned sealingdifliculties as regards tap changing devices associated withtransformers having bell-shaped covers.

In the following the invention will be explained in more detail, withreference to the accompanying drawing, which comprises FIG. 1 shows theinstallation of three tap changing devices in accordance with thepresent invention; and

FIG. 2 is a sectional view of a detail of this installation, on anenlarged scale.

In the drawing, a transformer tank is shown, with supporting columns,bell-shaped cover or hood, and details of the tap changing devices withtheir installation according to the present invention. In particular,numerals 10, 10', 10" denote three tap changing devices which arejointly mounted on a plate 2. Plate 2 in its turn rests on a framework 1which is supported by columns 3 resting on the transformer tank bottom.

As it is shown in FIG. 2, the ends of these columns 3 on the side of theframework 1 are formed as spindles 5 for raising and lowering theframework 1. 'By means of holes 8 in the transformer cover, thesespindles 5 may be readily operated. When the framework 1 is sufiicientlylifted, it is held together with a transformer 3,243,748 Patented Mar.29, 1966 "ice cover 11 by means of screws 6 and packings 4. The spindles5 are secured by means of nuts 7. Finally, numeral 9 denotes the sealingflange between the bell-shaped cover and the lower part of thetransformer tank.

Following the proposal of the present invention, the tap changingdevices 10, 10', 10 are entirely separate from the clamping structurefor the transformer core and the windings. Therefore, it is possible tomount the tap changing devices independent of and separate from thetransformer core.

In particular, the clamping structure may be tightened after heating upthe transformer core and coils, irrespective of the attachment of thetap changing devices. The

bell-shaped cover may readily be bolted to the lower part of thetransformer tank. A lever-difference between the cover and the framework1, possibly existing after the cover has been set up, may be correctedby raising the framework 1 to a rate corresponding to the height of thepackings 4, by means of the spindles 5. In other words, the framework 1supporting the tap changing devices 10, etc. is raised to the cover 11,by the intermediary of the spindles 5, to such an extent that thesealing screws 6 actually have to apply only the clamping pressure whenthese screws are subsequently tightened but are not bound to take partin supporting the tap changing devices by means of the framework 1. Thesupporting task is undertaken solely by the columns 3. In this wayreliable sealing of the tap changing device is guaranteed, even withtransformers having bellshaped covers.

What we claim is:

1. An oil-filled transformer having a tank with a bellshaped cover,apertures in the top thereof, and tap-changing devices mounted over saidapertures, a supporting installation comprising columns resting on thebottom of said tank, a framework attached to said columns and mountingsaid tap-changing devices, and adjusting means between said columns andsaid framework for regulating the height of said tap-changing deviceswith respect to said tank, said adjusting means including a spindlesupporting a portion of said framework from the free end of each column,and holes in said bell-shaped cover adjacent said spindles to permitaccess for adjustment thereof.

2. An installation as defined in claim 1, wherein said free column endsare formed into said spindles, said adjusting means further including atightening nut for each spindle.

3. An installation as defined in claim 1, further comprising a plateremovably attached to Said framework for releasably supporting saidtap-changing devices.

4. An installation as defined in claim 1, further comprising attachingmeans between said framework and peripheral portions of said coverprotruding thereabove.

5. An installation as defined in claim 4, further comprising packingmeans between said framework and said peripheral cover portions at leastin the region of said attaching means.

6. An installation as defined in claim 5, further comprising a sealingflange between said cover and lower portions of said tank.

References Cited by the Examiner UNITED STATES PATENTS 1,583,383 5/1926Bingay 336 -92 X 2,158,103 5/1939 Beyerle 336--92 X 2,479,330 8/1949Fagley 336-92 X ROBERT K. SCHAEFER, Primary Examiner.

JOHN F. BURNS, Examiner.

1. AN OIL-FILLED TRANSFORMER HAVING A TANK WITH A BELLSHAPED COVER,APERTURES IN THE TOP THEREOF, AND TAP-CHANGING DEVICES MOUNTED OVER SAIDAPERTURES, A SUPPORTING INSTALLATING COMPRISING COLUMNS RESTING ON THEBOTTOM OF TANK, A FRAMEWORK ATTACHED TO SAID COLUMNS AND MOUNTING SAIDTAP-CHANGING DEVICES, AND ADJUSTING MEANS BETWEEN SAID COLUMNS AND SAIDFRAMEWORK FOR REGULATING THE HEIGHT OF SAID TAP-CHANGING DEVICES WITHRESPECT TO SAID TANK, SAID ADJUSTING MEANS INCLUDING A SPINDLESUPPORTING A PORTION OF FRAMEWORK FROM THE FREE END OF EACH COLUMN, ANDHOLES IN SAID BELL-SHAPED COVER ADJACENT SAID SPINDLES TO PERMIT ACCESSFOR ADJUSTMENT THEREOF.